US4577111A - Apparatus for electron beam lithography - Google Patents

Apparatus for electron beam lithography Download PDF

Info

Publication number
US4577111A
US4577111A US06/516,091 US51609183A US4577111A US 4577111 A US4577111 A US 4577111A US 51609183 A US51609183 A US 51609183A US 4577111 A US4577111 A US 4577111A
Authority
US
United States
Prior art keywords
lens
electron beam
demagnifying
electrooptic
electrooptic means
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US06/516,091
Other languages
English (en)
Inventor
Norio Saitou
Susumu Ozasa
Takashi Matsuzaka
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Ltd
Original Assignee
Hitachi Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hitachi Ltd filed Critical Hitachi Ltd
Assigned to HITACHI, LTD., A CORP. OF JAPAN reassignment HITACHI, LTD., A CORP. OF JAPAN ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: MATSUZAKA, TAKASHI, OZASA, SUSUMU, SAITOU, NORIO
Application granted granted Critical
Publication of US4577111A publication Critical patent/US4577111A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
    • H01J37/10—Lenses
    • H01J37/14—Lenses magnetic
    • H01J37/141—Electromagnetic lenses
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
    • H01J37/3002—Details
    • H01J37/3007—Electron or ion-optical systems
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
    • H01J37/317—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation
    • H01J37/3174—Particle-beam lithography, e.g. electron beam lithography
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P95/00—Generic processes or apparatus for manufacture or treatments not covered by the other groups of this subclass
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/04—Means for controlling the discharge
    • H01J2237/045—Diaphragms
    • H01J2237/0451—Diaphragms with fixed aperture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/15—Means for deflecting or directing discharge
    • H01J2237/1505—Rotating beam around optical axis
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/15—Means for deflecting or directing discharge
    • H01J2237/152—Magnetic means
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/30—Electron or ion beam tubes for processing objects
    • H01J2237/304—Controlling tubes
    • H01J2237/30472—Controlling the beam
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/30—Electron or ion beam tubes for processing objects
    • H01J2237/317—Processing objects on a microscale
    • H01J2237/3175—Lithography
    • H01J2237/31776—Shaped beam

Definitions

  • the present invention relates to an apparatus for electron beam lithography using a shaped beam which is used for fabrication of integrated circuits or the like.
  • FIG. 1 shows the principle of this apparatus for lithography (see J. Vac. Sci. Technol., 19 (4), Nov./Dec. 1981, p.p. 1087 to 1093).
  • numeral 1 denotes an electron beam source
  • numerals 2 and 3 masks having square apertures
  • numerals 4 and 5 shaping lenses
  • numeral 7 a deflector
  • numerals 8 and 9 a demagnifying lens and a projection lens, respectively
  • numeral 10 a surface of a sample such as a wafer.
  • a square aperture 2' on the mask 2 is imaged onto the mask 3 by the two shaping lenses 4 and 5.
  • a shaped beam 6 for lithography is formed.
  • the size of this shaped beam 6 can be adjusted by the deflector 7 placed between the shaping lenses 4 and 5.
  • the shaped beam 6 is demagnified and imaged onto the sample face 10 by the demagnifying lens 8 and the projection lens 9.
  • the position of the shaped beam thus demagnified on the sample face 10 can be moved by a deflector 11 within the projection lens 9 in order to expose an arbitrary pattern.
  • FIGS. 2A and 2B illustrate the situation of pattern exposition.
  • FIG. 2A corresponds to ideal operation of the above-described apparatus for lithography.
  • Numeral 21 denotes the beam deflection range of the deflector 11, numeral 22 the direction of deflection, numeral 23 exposed patterns, and numeral 24 a shaped beam. If the direction of the shaped beam 24 is coincident with the direction of deflection 22 as illustrated in FIG. 2A, a desired pattern can be correctly exposed by successively connecting shaped beams.
  • FIG. 2B shows the exposed pattern obtained when these two directions are not coincident.
  • shaped beams are not aligned in the exposed pattern unless the two directions are coincident.
  • a lowered dimension accuracy of the pattern or an unsmooth boundary is incurred.
  • the square masks 2 and 3 have been mechanically rotated for squaring the direction of the shaped beam with that of deflection as described in Japanese Patent Application Laid-Open No. 57761/78.
  • this method it is impossible to square the center of the rotation axis with the center of the optical axis of the beam or the squared aperture.
  • the beam directed toward the sample face 10 is cut by the apertures for defining the beam existing on the way. This results in a drawback that the current density of the shaped beam becomes ununiformed.
  • such a method has a serious drawback that a long-time work by a prominent expert is required.
  • an object of the present invention is to provide an apparatus for electron beam lithography wherein the above-described drawbacks in the conventional apparatus for lithography are eliminated and the direction of the shaped beam may be readily adjusted without deteriorating the uniformness in the current density of that shaped beam.
  • an apparatus for lithography comprising a mask equipped with a polygonal aperture to be subjected to electron beam irradiation fed from an electron beam generator means, an electron lens system for demagnifying and imaging the polygonal aperture of the mask, and a solenoid lens for electron beam rotation adjustment placed between the mask and the final-stage electron lens.
  • FIG. 1 shows the principle of an apparatus for lithography
  • FIGS. 2A and 2B illustrate the relationship between a shaped beam and an exposed pattern
  • FIG. 3 shows an embodiment of an apparatus for lithography according to the present invention.
  • FIG. 4 shows the locus of an electron when a solenoid lens is operated.
  • a rotation angle ⁇ may be represented as ##EQU1## where e and m o are respectively the charge and mass of an electron, V the acceleration voltage, and B(z) the intensity of the magnetic field in the direction whereto the electron is running.
  • ⁇ is proportional to the excitation coefficient and may be represented as ##EQU2## where I is a current flowing through the solenoid, N the number of turns in the coil, and E the energy of an electron represented in the unit of eV. ##EQU3## ⁇ is approximately 1 rad.
  • the shaped beam is electromagnetically rotated using the above-described rotation effect.
  • FIG. 3 shows an embodiment of the present invention.
  • a solenoid lens 12 is placed in the space between the second shaping aperture (hereinafter abbreviated as aperture) 3 and the demagnifying lens 8 of the apparatus illustrated in FIG. 1.
  • aperture the second shaping aperture
  • demagnifying lens 8 the demagnifying lens 8 of the apparatus illustrated in FIG. 1.
  • Other numerals 1 to 11 denote the same components as FIG. 1.
  • the rotation angle of the shaped beam may be increased by increasing the excitation coefficient of the solenoid lens 12 placed as illustrated in FIG. 3. It is also possible to invert the rotation direction of the shaped beam by inverting the excitation direction.
  • the excitation of the solenoid lens 12 is made controllable from a controller for controlling other lenses, the excitation may be easily operated by an operator.
  • the solenoid lens 12 exerts not only a rotation effect but also a focusing effect upon the electron beam, the following restriction conditions are imposed on the focal distance of the solenoid 12.
  • the first condition is that the position of the focus must not be largely deviated when the solenoid lens is excited to rotate the shaped beam.
  • the second condition is that the beam axis deviation caused by excitation of the solenoid lens must fall within the permissible tolerance.
  • FIG. 4 shows the locus of an electron before and after the solenoid lens 12 in detail.
  • the shaped beam 6 which has been shaped by the aforementioned aperture is demagnified and imaged onto a point 31 by a demagnifying lens 8.
  • the demagnifying ratio is assumed to be 1/M.
  • the imaged point is deviated by ⁇ z.
  • the ⁇ z may be represented as ##EQU4## where l 1 denotes a distance from the aperture 3 to the center of the solenoid lens 12 and F denotes the focal distance of the solenoid lens 12.
  • L denotes a distance between the aperture 3 and the demagnifying lens 8.
  • F the relationship between F and L may be represented as ##EQU5##
  • the beam axis deviation under the excitation of the solenoid lens 12 is caused by the center of the solenoid lens 12 which is not coincident with an axis connecting the aperture 3 and the demagnifying lens 8. This deviation is denoted by h.
  • the crossover image of the electron beam source is focused at a point 32 near the front focus of the demagnifying lens 8.
  • the size of the image thus focused is close to the crossover diameter.
  • the deviation ⁇ r of the crossover image in the direction which is perpendicular to the axis is approximately represented as ##EQU6##
  • the expression (6) indicates the necessity of a small l 2 (which is opposite to a small ⁇ z), a small h and a large F. Assuming from the practical point of view that
  • Expressions (5) and (8) indicate that the focal distance F of the solenoid lens 12 must be at least five times as large as the distance L between the above described aperture 3 and the demagnifying lens 8. Since L is usually approximately 20 cm, F must be 1 m or more.
  • the solenoid lens used in the above-described embodiment is sometimes called as a rotation lens, a solenoid coil, a rotation coil or the like.
  • a demagnifying lens composed of one stage has been shown as an example.
  • a plurality of or multi-stage of demagnifying lenses may be used when the demagnification ratio must be made larger.
  • the above-described solenoid lens may be placed between arbitrary demagnifying lenses. That is to say, the solenoid lens may be arbitrarily placed between the above-described aperture and the final-stage demagnifying lens.
  • the described concept of the present invention may essentially be applied to a case where the solenoid is placed between the aperture and the projection lens or a case where the projection lens functions also as a demagnifying lens.
  • a shaped beam for lithography has been square shaped.
  • shape of a shaped beam is not restricted to a square.
  • a solenoid coil for electron beam rotation adjustment is placed between the mask and a final electron lens, thus realizing an apparatus for lithography wherein the direction of the shaped beam may be readily adjusted without deteriorating the uniformness in the current density of that shaped beam.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Nanotechnology (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Manufacturing & Machinery (AREA)
  • Mathematical Physics (AREA)
  • Theoretical Computer Science (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Electromagnetism (AREA)
  • Electron Beam Exposure (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
US06/516,091 1982-07-28 1983-07-22 Apparatus for electron beam lithography Expired - Lifetime US4577111A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP57131476A JPH0732108B2 (ja) 1982-07-28 1982-07-28 電子線露光装置
JP57-131476 1982-07-28

Publications (1)

Publication Number Publication Date
US4577111A true US4577111A (en) 1986-03-18

Family

ID=15058861

Family Applications (1)

Application Number Title Priority Date Filing Date
US06/516,091 Expired - Lifetime US4577111A (en) 1982-07-28 1983-07-22 Apparatus for electron beam lithography

Country Status (3)

Country Link
US (1) US4577111A (ja)
JP (1) JPH0732108B2 (ja)
GB (1) GB2125614B (ja)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1988002920A1 (en) * 1986-10-08 1988-04-21 Varian Associates, Inc. Method and apparatus for constant angle of incidence scanning in ion beam systems
US4804851A (en) * 1984-06-19 1989-02-14 Texas Instruments Incorporated Charged particle sources
EP0431864A3 (en) * 1989-12-04 1991-10-30 Fujitsu Limited Method of detecting and adjusting exposure conditions of charged particle exposure system
US5466904A (en) * 1993-12-23 1995-11-14 International Business Machines Corporation Electron beam lithography system
US5523580A (en) * 1993-12-23 1996-06-04 International Business Machines Corporation Reticle having a number of subfields
US5635719A (en) * 1996-07-23 1997-06-03 International Business Machines Corporation Variable curvilinear axis deflection means for particle optical lenses
US5674413A (en) * 1993-12-23 1997-10-07 International Business Machines Corporation Scattering reticle for electron beam systems
US5757010A (en) * 1996-12-18 1998-05-26 International Business Machines Corporation Curvilinear variable axis lens correction with centered dipoles
DE19911372A1 (de) * 1999-03-15 2000-09-28 Pms Gmbh Vorrichtung zum Steuern eines Strahls aus elektrisch geladenen Teilchen
US20080054196A1 (en) * 2006-09-06 2008-03-06 Elpida Memory, Inc. Variable shaped electron beam lithography system and method for manufacturing substrate

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2197751A (en) * 1986-11-24 1988-05-25 Philips Electronic Associated Variable shaped spot electron beam pattern generator
JP2843594B2 (ja) * 1989-03-20 1999-01-06 富士通株式会社 荷電粒子ビーム露光装置及びその露光方法
EP1777728A1 (en) 2005-10-20 2007-04-25 Carl Zeiss SMS GmbH Lithography system

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5445025A (en) * 1977-09-13 1979-04-10 Kyokuto Kaihatsu Kogyo Co Ltd Buffer device in packing case lifting mechanism of damp car
GB2005243A (en) * 1977-10-01 1979-04-19 Otsuka Chemical Co Ltd Metal corrosion inhibitor
JPS551186A (en) * 1979-04-23 1980-01-07 Toshiba Corp Electron beam exposure apparatus
US4182958A (en) * 1977-05-31 1980-01-08 Rikagaku Kenkyusho Method and apparatus for projecting a beam of electrically charged particles
JPS56152145A (en) * 1980-04-26 1981-11-25 Jeol Ltd Electron microscope
US4393310A (en) * 1978-01-19 1983-07-12 Eberhard Hahn Method of and device for adjusting a shaped-electron-beam working device

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2055243B (en) * 1979-08-01 1983-07-06 Zeiss Jena Veb Carl Method and device for tilting planar beam probes
JPS5741815A (en) * 1980-08-26 1982-03-09 Nippon Kokan Kk <Nkk> Controlling method for sheet shape in tandem rolling mill
JPS5773938A (en) * 1980-10-28 1982-05-08 Nippon Telegr & Teleph Corp <Ntt> Correcting apparatus for electron beam rotation on electro optical mirror

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4182958A (en) * 1977-05-31 1980-01-08 Rikagaku Kenkyusho Method and apparatus for projecting a beam of electrically charged particles
JPS5445025A (en) * 1977-09-13 1979-04-10 Kyokuto Kaihatsu Kogyo Co Ltd Buffer device in packing case lifting mechanism of damp car
GB2005243A (en) * 1977-10-01 1979-04-19 Otsuka Chemical Co Ltd Metal corrosion inhibitor
US4393310A (en) * 1978-01-19 1983-07-12 Eberhard Hahn Method of and device for adjusting a shaped-electron-beam working device
JPS551186A (en) * 1979-04-23 1980-01-07 Toshiba Corp Electron beam exposure apparatus
JPS56152145A (en) * 1980-04-26 1981-11-25 Jeol Ltd Electron microscope

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Variably Shaped Electron Beam Lithography System, EB55: 11 Electron Optics, Saitou et al., J. Vac. Sci. Tech., vol. 19, No. 4, Nov./Dec. 1981. *

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4804851A (en) * 1984-06-19 1989-02-14 Texas Instruments Incorporated Charged particle sources
WO1988002920A1 (en) * 1986-10-08 1988-04-21 Varian Associates, Inc. Method and apparatus for constant angle of incidence scanning in ion beam systems
EP0431864A3 (en) * 1989-12-04 1991-10-30 Fujitsu Limited Method of detecting and adjusting exposure conditions of charged particle exposure system
US5466549A (en) * 1989-12-04 1995-11-14 Fujitsu Limited Method of detecting and adjusting exposure conditions of charged particle exposure system
US5466904A (en) * 1993-12-23 1995-11-14 International Business Machines Corporation Electron beam lithography system
US5523580A (en) * 1993-12-23 1996-06-04 International Business Machines Corporation Reticle having a number of subfields
US5674413A (en) * 1993-12-23 1997-10-07 International Business Machines Corporation Scattering reticle for electron beam systems
US5635719A (en) * 1996-07-23 1997-06-03 International Business Machines Corporation Variable curvilinear axis deflection means for particle optical lenses
US5757010A (en) * 1996-12-18 1998-05-26 International Business Machines Corporation Curvilinear variable axis lens correction with centered dipoles
DE19911372A1 (de) * 1999-03-15 2000-09-28 Pms Gmbh Vorrichtung zum Steuern eines Strahls aus elektrisch geladenen Teilchen
US20080054196A1 (en) * 2006-09-06 2008-03-06 Elpida Memory, Inc. Variable shaped electron beam lithography system and method for manufacturing substrate
US7714308B2 (en) * 2006-09-06 2010-05-11 Elpida Memory, Inc. Variable shaped electron beam lithography system and method for manufacturing substrate

Also Published As

Publication number Publication date
GB2125614B (en) 1986-02-05
GB2125614A (en) 1984-03-07
GB8319949D0 (en) 1983-08-24
JPS5922326A (ja) 1984-02-04
JPH0732108B2 (ja) 1995-04-10

Similar Documents

Publication Publication Date Title
US4967088A (en) Method and apparatus for image alignment in ion lithography
US4577111A (en) Apparatus for electron beam lithography
US4243866A (en) Method and apparatus for forming a variable size electron beam
US6037601A (en) Electron beam illumination device, and exposure apparatus with electron beam illumination device
JPH09223475A (ja) 電磁偏向器、及び該偏向器を用いた荷電粒子線転写装置
JPH025010B2 (ja)
US4112305A (en) Method of projecting a beam of charged particles
US5316879A (en) Sub-micron device fabrication using multiple aperture filter
JPH02125609A (ja) 半導体製造装置
US4859857A (en) Ion-projection apparatus and method of operating same
US5350924A (en) Ion-optical imaging system
US6455863B1 (en) Apparatus and method for forming a charged particle beam of arbitrary shape
US5376505A (en) Device fabrication entailing submicron imaging
EP0035556B1 (en) Electron beam system
US5663568A (en) Apparatus for controlling a charged particle beam and a lithographic process in which the apparatus is used
US5847402A (en) Charged particle beam pattern transfer apparatus and method
US5436460A (en) Ion-optical imaging system
GB1587852A (en) Electron beam apparatus
US5989753A (en) Method, apparatus, and mask for pattern projection using a beam of charged particles
JP2000100364A (ja) 荷電粒子線転写装置
JPH11176720A (ja) 電子ビーム露光装置
JPH06338445A (ja) 電子ビーム描画装置
JP2001118765A (ja) 荷電粒子線露光装置、荷電粒子線露光装置の調整方法及び半導体デバイスの製造方法
JP3531323B2 (ja) イオンビーム加工方法および装置
JPH1070059A (ja) 荷電粒子線転写装置

Legal Events

Date Code Title Description
AS Assignment

Owner name: HITACHI, LTD., 6, KANADA SURUGADAI 4-CHOME, CHIYOD

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:SAITOU, NORIO;OZASA, SUSUMU;MATSUZAKA, TAKASHI;REEL/FRAME:004156/0961

Effective date: 19830713

Owner name: HITACHI, LTD., A CORP. OF JAPAN,JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SAITOU, NORIO;OZASA, SUSUMU;MATSUZAKA, TAKASHI;REEL/FRAME:004156/0961

Effective date: 19830713

STCF Information on status: patent grant

Free format text: PATENTED CASE

FPAY Fee payment

Year of fee payment: 4

FEPP Fee payment procedure

Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

FPAY Fee payment

Year of fee payment: 8

FPAY Fee payment

Year of fee payment: 12